​DIAS next seminar will be presented by Dr. Valentina Magni from the Centre of Earth Evolution and Dynamics (CEED), University of Oslo. Her talk will be about the role of mantle flow in arc and back-arc magmatism.

Abstract: I use three-dimensional numerical models of oceanic and continental subduction to investigate how melt production evolves in different regions of a subduction zone. Particular focus is put on tracking the mantle flow to understand where the mantle material that is the source of melting at the arc and back-arc comes from. My results show that, when the back-arc basin forms, the melting regions beneath the arc and the back-arc are connected to each other. These two regions get further apart as subduction continues and the slab keeps retreating. Interestingly, at this stage, the mantle that flows beneath the arc comes from the back-arc region where it has been already partially depleted. Therefore, for about 10 Myrs, during the spreading phase at the back-arc, arc magmatism is reduced and has a more depleted source. Eventually the arc and back-arc spreading regions get so far apart that the mantle flow pattern gets back to the more classic corner flow advection cell that does not sample any depleted mantle source before reaching the mantle wedge. These models can help explaining the spatial and temporal geochemical variations of lavas along the arc.